I am also getting this issue. On first entry to the custom venue, most turn up (not all). When the schedule changes (eg, I have a custom venue that is a cafe from 6am-7pm, a lounge from 7pm - 10 pm and a nightclub from 10pm-6am) from cafe, to lounge, then to nightclub, only about five or so sims show up. (this also occurs if I switch to another sim in another world and then switch back to the sim at the venue - suddenly the large group leaves and a small group of about five sims only appears). (I have resorted to hiring staff by clicking on the DJ booth & bars, but this costs simoleons so it is not ideal, nor a solution)
Additionally, Sims requested to fill roles are not turning up, or if they do (like the barista), they don't actually do as they are told.
I am on pc, I have not used mods in a few months now.
